1. Field of the Invention
The present invention relates to an ignition controller which is applied to a vehicle engine.
2. Description of the Related Art
As well known, a vehicle engine is provided with an ignition-timing adjusting means. The ignition-timing adjusting means functions to advance the ignition timing as the rotational speed of the engine increases.
Meanwhile, such a vehicle as, for example, a racing motor bycycle is mounted with a high output engine. In the case of such a racing two-wheel vehicle, when the vehicle is running with a speed shift gear set at a high speed stage, the engine output must be maximum; whereas, when the shift gear is set at an intermediate speed stage, the engine output must be relatively high for acceleration. When the shift gear is set at the first speed stage as at the time of starting the vehicle or when the vehicle is running along a sharply curved road, it is unnecessary for the engine output to be very high.
The conventional ignition-timing adjusting means has no function of suppressing the engine output when the shift gear is set at the first speed stage. Therefore, when the racing vehicle or the like is running with the shift gear set at the first speed stage, the engine output becomes excessively high. For this reason, the rider has had to carefully adjust the opening of an accelerator to obtain comfortable acceleration.
Meanwhile, in the case of such a two wheeler, it is dangerous to increase the vehicle speed limitlessly.
To this end, there has been suggested an ignition controller which reduce the number of ignition times for the engine when the vehicle speed exceeds a preset vehicle speed limit (allowable maximum vehicle speed).
In this ignition controller, ignition is carried out according to such an ignition pattern as exemplified in FIG. 22 when the vehicle speed exceeds the aforementioned vehicle speed limit.
In the above ignition pattern, which is applied to a 4-cylinder engine, #1, #2 and #4 cylinders of the four cylinders are misfired respectively once per two times. In other words, the engine is ignited at a misfire rate of 3/8. In FIG. 22, mark .largecircle. denotes ignition and mark .times. denotes misfiring respectively.
When ignition is effected according to the aforementioned ignition pattern, the vehicle speed can be quickly decreased so that acceleration and deceleration are repeated at a short period. That is, a hunting phenomenon takes place in the engine rotational speed nearly at an engine rotational speed N.sub.a corresponding to a control vehicle speed.
For this reason, the prior art ignition controller has had such a disadvantage that, when such an ignition pattern as mentioned above is used, rider's running comfortableness is deteriorated.
In FIG. 21, reference symbol N.sub.b represents a preset rotational speed somewhat lower than the rotational speed N.sub.a, symbol a represents an increasing part in the engine rotational speed during ordinary ignition having a misfire rate of zero, and b represents a decreasing part in the engine rotational speed while ignition is effected based on the above ignition pattern, respectively.
In the case where the motor bicycle is, for example, of a 750 cc class, sports type, even when the transmission is set at a relatively low speed stage, the motor bicycle can run at a high speed.
More in detail, in the case where the transmission of the motor bicycle has first to sixth speed stages, the motor bicycle reaches the allowable maximum vehicle speed (vehicle speed limit) V.sub.A during running of the vehicle set, for example, at the fourth speed stage, as shown in FIG. 23. Under such a condition, even when the speed stage is shifted up from the fifth speed stage to the sixth, the vehicle speed will not increase.
When the driver shifts up the shift gear, he expects that the vehicle will be accelerated. For this reason, with the prior art ignition controller, such driver's expection is belied, which is one of factors deteriorating his driving comfortableness.